botan: disable AltiVec if the CPU does not support it

Botan compiles all PowerPC code with AltiVec support and only determines
at runtime whether the CPU even supports it. If the target CPU uses the
older SPE extensions, though, this is too late; since SPE and AltiVec
are incompatible, gcc aborts the compilation. This patch explicitly
disables AltiVec support unless BR2_POWERPC_CPU_HAS_ALTIVEC is defined

Signed-off-by: Tobias Blass <tobias.blass@rohde-schwarz.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
(cherry picked from commit e654839f9e2cc6d2780916d0288941cb3d4555dd)
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/botan/botan.mk

@@ -43,6 +43,12 @@ BOTAN_DEPENDENCIES += zlib
 BOTAN_CONF_OPTS += --with-zlib
 endif
 
+ifeq ($(BR2_POWERPC_CPU_HAS_ALTIVEC),y)
+BOTAN_CONF_OPTS += --enable-altivec
+else
+BOTAN_CONF_OPTS += --disable-altivec
+endif
+
 define BOTAN_CONFIGURE_CMDS
 	(cd $(@D); $(TARGET_MAKE_ENV) ./configure.py $(BOTAN_CONF_OPTS))
 endef